System and method for selectively post-curing parts printed with stereolithography additive manufacturing techniques

ABSTRACT

The present subject matter is directed towards a system and a method for selectively post-curing a three-dimensional (3D-printed) object to attain variable properties. The system comprises a selective post-curing chamber coupled to a computer in communication with a database for accessing a digital model or data concerning the 3D-printed object. The chamber comprises a movable light source assembly and a mounting platform for supporting at least one 3D-printed object thereon. The computer includes one or more executable instructions for selectively emitting a curing light onto the 3D-printed object along a predetermined curing toolpath based on the digital model. The curing of the 3D-printed object along the predetermined curing toolpath generates variable properties along different regions of the 3D-printed object.

PRIORITY AND RELATED APPLICATIONS

This application is a continuation of U.S. nonprovisional applicationSer. No. 17/902,221, filed on Sep. 2, 2022, which is a continuation ofU.S. nonprovisional application Ser. No. 17/511,881, filed on Oct. 27,2021, which claims priority to U.S. Provisional Application No.63/083,772, filed on filed on Sep. 25, 2020, the disclosure of which areincorporated by reference in their entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to stereolithography additivemanufacturing. More specifically, the present invention relates toselectively post curing parts that have been printed withstereolithography additive manufacturing techniques.

COPYRIGHT AND TRADEMARK NOTICE

A region of the disclosure of this patent application may containmaterial that is subject to copyright protection. The owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightswhatsoever.

Certain marks referenced herein may be common law or registeredtrademarks of third parties affiliated or unaffiliated with theapplicant or the assignee. Use of these marks is by way of example andshould not be construed as descriptive or to limit the scope of thisinvention to material associated only with such marks.

BACKGROUND OF THE INVENTION

One of the challenges of three-dimensional (3D) printing usingstereolithography is that the generated 3D objects generally comprise ofuniform material properties. That is, because of the current limitationsand or techniques involved in 3D printing 3D objects, it has not beenpossible to generate or print certain 3D objects with varying materialproperties, which may be desirable for some applications. For example,stereolithography is one of the commonly used techniques for printingparts in many industries including dentistry. In dentistry, it may bedesirable to create or print a 3D object with a variable color shade,with a variable opacity, or with other variable material properties.

Currently, once a part or 3D object is printed, the 3D object istypically post cured in a curing chamber with a massive amount of energyto achieve the desired and formulated properties. However, this processdoes not result in a 3D object with variable properties. Therefore,there is a need for a system and method that addresses theseshortcomings, and it is to these ends that the present invention hasbeen developed.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, a system and method is described forselectively post curing three-dimensionally (3D) printed objects thathave been printed with stereolithography additive manufacturingtechniques, to create a cured 3D-printed object with variableproperties. These variable properties may include, without limitation, avariable color shade, a variable opacity, variable flexural strengths,variable modulus, or other variable material properties that may beachieved via post-curing means.

In some exemplary embodiments, the invention involves a system forselectively post-curing a 3D-printed object to attain variableproperties. This system may include: a processing module for receivingdata concerning the 3D-printed object and determining a curing toolpathconfigured to achieve a post-cured 3D-printed object having variableproperties along different regions of the 3D-printed object; and aselective post-curing module, including a chamber with a light sourceconfigured to house the 3D-printed object and selectively emitting acuring light onto the 3D-printed object.

In some exemplary embodiments, a system for selectively post-curing a3D-printed object to attain variable properties may include: a selectivepost-curing chamber adapted to receive a 3D-printed object; apost-curing light source housed in the selective post-curing chamber;and a computer coupled to the post-curing light source including one ormore executable instructions for selectively emitting a curing lightonto the 3D-printed object along a predetermined curing toolpath basedon data of the 3D-printed object, wherein curing the 3D-printed objectalong the predetermined curing toolpath generates variable propertiesalong different regions of the 3D-printed object.

In some exemplary embodiments, a method for selectively post-curing a3D-printed object to attain variable properties may include the stepsof: receiving data concerning a 3D-printed object; determining a curingtoolpath configured to achieve a post-cured 3D object having variableproperties along different regions of the 3D-printed object; andselectively emitting a curing light onto the 3D-printed object along thecuring toolpath, wherein curing the 3D-printed object along the curingtoolpath generates the variable properties along the different regionsof the 3D-printed object.

In some exemplary embodiments, a method for selectively post-curing a3D-printed object to attain variable properties may include the stepsof: mounting a 3D-printed object in a selective post-curing chamberincluding a post-curing light source configured to emit a curing lightonto the 3D-printed object; receiving data of the 3D-printed objectconcerning a curing toolpath; and selectively emitting a curing lightonto the 3D-printed object along the curing toolpath based on the modeldata, wherein curing the 3D-printed object along the curing toolpathgenerates variable properties along different regions of the 3D-printedobject.

In some exemplary embodiments, the invention involves a system forselectively post-curing a 3D-printed object to attain variableproperties. The system may comprise: a chamber; a platform arrangedwithin the chamber for supporting at least one 3D-printed object; alight source assembly arranged within the chamber and configured to emitone or more wavelengths of a curing light onto the 3D-printed object; amovement module configured to move the light source assembly or theplatform in order to selectively expose different regions of the3D-printed object to the curing light along a predetermined curing pathof the 3D-printed object; and a processing module in communication withthe light source assembly and the movement module, the processing moduleincluding one or more executable instructions configured to: receive auser input concerning the 3D-printed object, the user input indicativeof the curing path for post-curing the 3D-printed object; move the lightsource assembly or the platform according to the curing path; and emitthe curing light onto the 3D-printed object along the curing toolpath tocreate a post-cured 3D-printed object.

In some exemplary embodiments, the system may comprise: a chamber; aplatform arranged within the chamber for supporting at least one3D-printed object; a light source assembly arranged within the chamberand configured to emit one or more wavelengths of a curing light ontothe 3D-printed object, wherein the light source assembly includes atleast one light source disposed above the platform and at least onelight source disposed below the platform; a movement module configuredto move the light source assembly or the platform in order toselectively expose different regions of the 3D-printed object to thecuring light along a predetermined curing path of the 3D-printed object;and a processing module in communication with the light source assemblyand the movement module, the processing module including one or moreexecutable instructions configured to: receive a user input concerningthe 3D-printed object, the user input indicative of the curing path forpost-curing the 3D-printed object; move the light source assembly or theplatform according to the curing path; and emit the curing light ontothe 3D-printed object along the curing toolpath to create a post-cured3D-printed object.

Various objects and advantages of the present invention will becomeapparent from the following description taken in conjunction with theaccompanying drawings wherein are set forth, by way of illustration andexample, certain embodiments of this invention. The drawings submittedherewith constitute a part of this specification, include exemplaryembodiments of the present invention, and illustrate various objects andfeatures thereof.

BRIEF DESCRIPTION OF DRAWINGS

Elements in the figures have not necessarily been drawn to scale inorder to enhance their clarity and improve understanding of thesevarious elements and embodiments of the present invention. Furthermore,elements that are known to be common and well understood to those in theindustry are not depicted in order to provide a clear view of thevarious embodiments of the invention.

FIG. 1 exemplarily illustrates a system for selectively post-curing athree-dimensional object to attain variable properties, according to anembodiment of the present invention.

FIG. 2A exemplarily illustrates a block diagram of a system forselectively post-curing a three-dimensional object to attain variableproperties in communication with the database and 3-D scanner, accordingto an embodiment of the present invention.

FIG. 2B exemplarily illustrates a block diagram of a chamber forselectively post-curing a three-dimensional object, according to anembodiment of the present invention.

FIG. 3 exemplarily illustrates a method for selectively post-curing athree-dimensional object to attain variable properties, according topractice of some embodiments of the present invention.

FIG. 4A exemplarily illustrates a perspective view of a post-curingchamber, according to an embodiment of the present invention.

FIG. 4B exemplarily illustrates a perspective view of a motion systemand a light source assembly of the post-curing chamber, according to anembodiment of the present invention.

FIG. 4C exemplarily illustrates a top view of a motion system and alight source assembly of the post-curing chamber, according to anembodiment of the present invention.

FIG. 4D exemplarily illustrates a rear view of a motion system and alight source assembly of the post-curing chamber, according to anembodiment of the present invention.

FIG. 4E exemplarily illustrates a side view of a motion system and alight source assembly of the post-curing chamber, according to anembodiment of the present invention.

FIG. 5 exemplarily illustrates an exploded view of the light sourceassembly, according to an embodiment of the present invention.

FIG. 6 exemplarily illustrates a perspective view of thermal managementsystem of the post-curing chamber, according to an embodiment of thepresent invention.

FIG. 7 exemplarily illustrates a heating element arranged in thepost-curing chamber, according to an embodiment of the presentinvention.

FIG. 8 exemplarily illustrates an exploded view of the heating elementof the post-curing chamber, according to an embodiment of the presentinvention.

FIG. 9A exemplarily illustrates a front view of the post curing chamber,according to an embodiment of the present invention.

FIG. 9B exemplarily illustrates a perspective view of the post curingchamber, according to an embodiment of the present invention.

FIG. 9C exemplarily illustrates a perspective view of the post curingchamber and the tray system, according to an embodiment of the presentinvention.

FIG. 9D exemplarily illustrates a side view of the post curing chamberand tray system, according to an embodiment of the present invention.

FIG. 9E exemplarily illustrates a front view of the post curing chamber,according to an embodiment of the present invention.

FIG. 9F exemplarily illustrates a top view of the post curing chamberand tray system, according to an embodiment of the present invention.

FIG. 9G exemplarily illustrates a perspective view of a front cover andpanel of the post curing chamber, according to an embodiment of thepresent invention.

FIG. 10 exemplarily illustrates a graph of radiation patterns for a postcuring system, according to an embodiment of the present invention.

FIG. 11 exemplarily illustrates a graph of radiation patterns for a postcuring system, according to another embodiment of the present invention.

FIG. 12 exemplarily illustrates a graph of relative intensity of lightsource of bottom and top panel, according to an embodiment of thepresent invention.

FIG. 13 exemplarily illustrates a graph of energy absorption for a postcuring system, according to an embodiment of the present invention.

FIG. 14 exemplarily illustrates a graph for absorbance of UVC by e-colibacteria, according to an embodiment of the present invention.

FIG. 15 exemplarily illustrates a graph of UVC intensity of the postcuring system, according to an embodiment of the present invention.

FIG. 16 exemplarily illustrates a graph of UVC intensity of the postcuring system, according to another embodiment of the present invention.

FIG. 17 exemplarily illustrates a graph for thermal resistance andairflow temperature, according to an embodiment of the presentinvention.

FIG. 18 is a graph showing relation between airflow and heatdissipation, according to an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

In the following discussion that addresses a number of embodiments andapplications of the present invention, reference is made to theaccompanying drawings that form a part thereof, where depictions aremade, by way of illustration, of specific embodiments in which theinvention may be practiced. It is to be understood that otherembodiments may be utilized, and changes may be made without departingfrom the scope of the invention. Wherever possible, the same referencenumbers are used in the drawings and the following description to referto the same or similar elements.

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant teachings. However, it should be apparent to those skilledin the art that the present teachings may be practiced without suchdetails. In other instances, well known structures, components and/orfunctional or structural relationship thereof, etc., have been describedat a relatively high-level, without detail, in order to avoidunnecessarily obscuring aspects of the present teachings.

Throughout the specification and claims, terms may have nuanced meaningssuggested or implied in context beyond an explicitly stated meaning.Likewise, the phrase “in one embodiment/example” as used herein does notnecessarily refer to the same embodiment and the phrase “in anotherembodiment/example” as used herein does not necessarily refer to adifferent embodiment. It is intended, for example, that claimed subjectmatter include combinations of example embodiments in whole or in part.

Conditional language used herein, such as, among others, “can,” “could,”“might,” “may,” “e.g.,” and the like, unless specifically statedotherwise, or otherwise understood within the context as used, isgenerally intended to convey that certain embodiments include, whileother embodiments do not include, certain features, elements and orsteps. Thus, such conditional language is not generally intended toimply that features, elements and or steps are in any way required forone or more embodiments, whether these features, elements and or stepsare included or are to be performed in any particular embodiment.

The terms “comprising,” “including,” “having,” and the like aresynonymous and are used inclusively, in an open-ended fashion, and donot exclude additional elements, features, acts, operations and soforth. Also, the term “or” is used in its inclusive sense (and not inits exclusive sense) so that when used, for example, to connect a listof elements, the term “or” means one, some, or all of the elements inthe list. Conjunctive language such as the phrase “at least one of X, Y,and Z,” unless specifically stated otherwise, is otherwise understoodwith the context as used in general to convey that an item, term, etc.may be either X, Y, or Z. Thus, such conjunctive language is notgenerally intended to imply that certain embodiments require at leastone of X, at least one of Y, and at least one of Z to each be present.The term “and or” means that “and” applies to some embodiments and “or”applies to some embodiments. Thus, A, B, and or C can be replaced withA, B, and C written in one sentence and A, B, or C written in anothersentence. A, B, and or C means that some embodiments can include A andB, some embodiments can include A and C, some embodiments can include Band C, some embodiments can only include A, some embodiments can includeonly B, some embodiments can include only C, and some embodimentsinclude A, B, and C. The term “and or” is used to avoid unnecessaryredundancy. Similarly, terms, such as “a, an,” or “the,” again, may beunderstood to convey a singular usage or to convey a plural usage,depending at least in part upon context. In addition, the term “basedon” may be understood as not necessarily intended to convey an exclusiveset of factors and may, instead, allow for existence of additionalfactors not necessarily expressly described, again, depending at leastin part on context.

While exemplary embodiments of the disclosure may be described,modifications, adaptations, and other implementations are possible. Forexample, substitutions, additions, or modifications may be made to theelements illustrated in the drawings, and the methods described hereinmay be modified by substituting, reordering, or adding stages to thedisclosed methods. Thus, nothing in the foregoing description isintended to imply that any particular feature, characteristic, step,module, or block is necessary or indispensable. Indeed, the novelmethods and systems described herein may be embodied in a variety ofother forms; furthermore, various omissions, substitutions, and changesin the form of the methods and systems described herein may be madewithout departing from the spirit of the invention or inventionsdisclosed herein. Accordingly, the following detailed description doesnot limit the disclosure. Instead, the proper scope of the disclosure isdefined by the appended claims.

As used in this disclosure, the term “comprise” and variations of theterm, such as “comprising” and “comprises”, are not intended to excludeother additives, components, integers or steps. For purpose ofdescription herein, the terms “upper”, “lower”, “left”, “right”,“front”, “rear”, “horizontal”, “vertical” and derivatives thereof shallrelate to the invention as oriented in figures. However, it is to beunderstood that the invention may assume various alternativeorientations and step sequences, except where expressly specified to thecontrary. It is also to be understood that the specific devices andprocesses illustrated in the attached drawings and described in thefollowing specification are simply exemplary embodiments of theinventive concepts defined in the appended claims. Hence, specificdimensions and other physical characteristic relating to the embodimentsdisclosed herein are not to be considered as limiting, unless the claimsexpressly state otherwise.

Turning now to the figures, FIG. 1 is a block diagram for a system 100in accordance with some exemplary embodiments of the present invention.More specifically, FIG. 1 depicts system 100, which typically includes a3D printing module 106 configured to print 3D objects, a processingmodule 102 configured to determine or store model data concerning the3D-printed object, including for example data concerning desirableproperties of the 3D-printed object such as desirable variableproperties that may be generated by curing the 3D-printed object, anddata concerning a curing path for post-curing the 3D-printed object toachieve the desired variable properties. Moreover, system 100 includes aselective post-curing module 104, which is configured to cure the3D-printed object after the 3D-printed object has been printed.

The processing module 102 typically receives data concerning the3D-printed object and may be configured to determine a curing toolpathconfigured to achieve a post-cured 3D-printed object having variableproperties along different regions of the 3D-printed object. This may beperformed in any number of ways, including for example by incorporatinga 3-D scanner 208, shown in FIG. 2 , that scans the object to receivedata for post-curing. In other embodiments, the data may be loaded ontothe processing module 102 directly from a database 204, shown in FIG. 2, that was used to fabricate the 3D-printed object. The model data mayinclude, without limitation, data concerning the structure of the3D-printed object, as well as desired properties subject of thepost-curing process. The desired or target variable properties for thepost-curing 3D-printed object may include, without limitation, avariable color shade, a variable opacity, variable flexural strengths,variable modulus, or other variable material properties that may beachieved via post-curing means. For example, variable color shades areideal for multicolor dental restorations such as crowns and bridges.Similarly, variable opacity may be ideal for multicolor dentalrestorations such as crowns and bridges. Furthermore, variable materialproperties such as various flexural strengths and modulus may be idealfor dental appliances such as orthodontic appliances, including—forexample and without limiting the scope of the present invention—alignersand retainers as well as occlusal guards and splints. Typically, theprocessing module 102 controls components of the selective post-curingmodule 104, which as will be discussed below, is configured to create apost-cured 3D-printed object having the target variable properties.

The selective post-curing module 104 typically includes a selectivepost-curing chamber 400 (hereinafter, also referred as chamber 400) witha light source configured to generate a powerful laser for thepost-curing process. The chamber 400 may include a mounting platform formounting the 3D-printed object once it comes out of the printing processfrom the 3D-printing module 106. In exemplary embodiments, the lightsource may include a projector mounted on a track that is configured torevolve around a mount within the chamber in which the 3D-printed objectis mounted. In this way, once the geometry of the 3D-printed object orpart that needs to be cured is out or ready from the 3D-printing module106, the pattern of energy will be projected onto the 3D-printed objectusing the projector equipped with the adequate wavelengths and energyamounts.

The 3D-printing module 106 may include any number of components such asthose that may be necessary or useful for stereolithography additivemanufacturing techniques. In exemplary embodiments, a database of the3D-printing module 106 may communicate with the processing module 102 ofthe present invention in order to provide the data for the curingtoolpath.

Accordingly, in some exemplary embodiments, a system 100 for selectivelypost-curing a 3D-printed object to attain variable properties mayinclude: a processing module 102 for receiving data concerning the3D-printed object and determining a curing toolpath configured toachieve a post-cured 3D-printed object having variable properties alongdifferent regions of the 3D-printed object; and a selective post-curingmodule 104, including a chamber with a light source configured to housethe 3D-printed object and selectively emitting a curing light onto the3D-printed object. In some exemplary embodiments, processing module 102receives data concerning the 3D-printed object, which includes apredetermined curing toolpath configured to achieve a post-cured3D-printed object having variable properties along different regions ofthe 3D-printed object. In some exemplary embodiments, a user interfacein communication with the module 104 enables a user to select the typeof 3D-printed object placed in the curing camber of the 400; theprocessing module will access data concerning the 3D-printed objectbased on the user-selection, the data including a predetermined curingtoolpath for the 3D-printed object, wherein the toolpath is configuredto post-cure the 3D-printed object into a post-cured 3D-printed objecthaving variable properties along different regions of the post-cured3D-printed object. As will be explained in more detailed below,post-curing the post-cured 3D-printed object with variable propertiesalong different regions of the post-cured 3D-printed object may beachieved by a movable light source assembly inside chamber 400.

In exemplary embodiments, the movable light source assembly may beconfigured to emit curing light at multiple wavelengths and at variablepositions along a movement track about a platform within the chamber400, such that the movable light source assembly emits curing light atone or more wavelengths onto a 3D-printed object along a predeterminedtoolpath associated with the 3D-printed object. The wavelength of thecuring light emitted onto the object may be variable; as such, avariable energy pattern may be emitted onto the 3D-printed object alongthe toolpath in accordance with a target physical property at a givenposition along the toolpath; in this way, the post-cured 3D-printed mayhave—by way of example and without limitation—a variable color shade, avariable opacity, a variable flexural strength, a variable elasticity, avariable modulus, or other variable material properties along thepredetermined toolpath.

Turning now to the next figure, FIG. 2A illustrates an exemplary system200 in accordance with some embodiments of the present invention. Morespecifically, FIG. 2A depicts system 200, which generally includes aselective post-curing chamber 400 adapted to receive a 3D-printedobject, a post-curing light source or movable light source assembly 202(that may include, for example an LED module) housed in the chamber 400,and a computer 206 coupled to the movable light source assembly 202including one or more executable instructions for selectively emitting acuring light onto the 3D-printed object along a predetermined curingtoolpath based on data of the 3D-printed object.

The chamber 400 may be any suitable curing chamber for curing 3D-printedobjects. The chamber 400 is typically adapted to house a 3D-printedobject that can be secured to an interior of the chamber 400 via amounting platform or mount suitable for holding the 3D-object in placeduring the curing process. In some exemplary embodiments, a track orpath may be provided around the mounting platform for the 3D-printedobject, in order to facilitate a rotation or revolution of the movablelight source assembly 202 around the 3D-printed object during thepost-curing process.

The computer 206 is generally coupled to or in communication with themovable light source assembly 202 and configured with one or moreexecutable instructions for selectively emitting a curing light onto the3D-printed object along a predetermined curing toolpath based on data ofthe 3D-printed object, wherein curing the 3D-printed object along thepredetermined curing toolpath generates variable properties alongdifferent regions of the 3D-printed object. To obtain the data, asmentioned above, the computer 206 may be coupled to or in communicationwith a database 204, such as a database of a 3D-printing module, oralternatively, or optionally, the computer 206 may be coupled to a 3Dscanner 208 that implements 3D scanning technologies in order to derivedata concerning the 3D-printed object.

In exemplary embodiments, the computer 206 includes one or moreexecutable instructions for: receiving data concerning a 3D-printedobject; determining a curing toolpath configured to achieve a post-cured3D-printed object having variable properties along different regions ofthe 3D-printed object; and selectively emitting a curing light onto the3D-printed object along the curing toolpath, wherein curing the3D-printed object along the curing toolpath generates the variableproperties along the different regions of the 3D-printed object. In someexemplary embodiments, computer 206 includes a user interface (i.e., akeyboard, a touch interface, a keypad, etc.) that enables a user toselect the type of 3D-printed object placed in the curing camber of the400; the computer will access data concerning the 3D-printed object(i.e., from scanner 208 or database 204) based on the user-selection,the data including a predetermined curing toolpath for the 3D-printedobject, wherein the toolpath is configured to post-cure the 3D-printedobject into a post-cured 3D-printed object having variable propertiesalong different regions of the post-cured 3D-printed object.

FIG. 2B exemplarily illustrates a block diagram of a chamber forselectively post-curing a three-dimensional object, according to anembodiment of the present invention. More specifically, FIG. 2B depictsexemplary system 500 for system for selectively post-curing a 3D-printedobject to attain one or more variable properties; system 500 may includethe same general components of system 200 as illustrated in FIG. 2A, butmay particularly include: a chamber 501; a platform 502 arranged withinthe chamber 501 for supporting at least one 3D-printed object thereon; acuring light module 503 such as a light source assembly arranged withinthe chamber 501 and configured to emit one or more wavelengths of acuring light onto the 3D-printed object; a movement module 504configured to move the curing light module 503 or the platform 502 inorder to selectively expose different regions of the 3D-printed objectto the curing light along a predetermined curing toolpath of the3D-printed object; and a processing module 505, which is incommunication with the curing light module 503 and the movement module504, the processing module 505 including one or more executableinstructions configured to: receive a user input, via a user interface505 a coupled to the processing module 505, the user input concerningthe 3D-printed object and indicative of the predetermined curingtoolpath for post-curing the 3D-printed object; move the curing lightmodule 503 or the platform 502 according to the curing toolpath; andemit the curing light onto the 3D-printed object along the curingtoolpath to create a post-cured 3D-printed object.

Chamber 501 may be constructed of various materials, although typicallya construction employs a design that provides insulation 501 a, such asfor example, insulation layers of insulating materials, as well as amultiple encasing construction that facilitates conservation of adesired temperature within the chamber but prevents excessive heatexposure to an outside of the chamber so as to protect the user. Inexemplary embodiments, the chamber comprises an interior surface finishadapted to maximize a reflectance for ultraviolet light. In exemplaryembodiments, in addition to insultation 501 a, chamber 501 may include athermal control module 501 b such as a heating device that may besituated below the platform 502 to expose the 3D-printed objects insidechamber 501 to a desired temperature suitable for the post-curingprocess.

Platform 502 may be any platform suitable for exposure to curing lightfrom curing light module 503, such as ultraviolet light, and suitablefor supporting one or more (and preferably although not necessarily)multiple 3D-printed objects within the chamber 501. In exemplaryembodiments, the platform may be stationary when chamber 501 is activebut may be movable to facilitate removal and insertion of the objectsinto and out of the chamber. In some exemplary embodiments, the platform502 may be a movable platform such as a rotating platform—for example aturntable platform. In some exemplary embodiments, the platform may be amovable platform that is capable of tilting or performing othermovements in order to facilitate adequate exposure of the 3D-printedobjects to the curing light from the curing light module 503. In someexemplary embodiments, platform 502 is a simple stationary platformsituated inside the chamber 501 in a manner such as to adequately exposea 3D-printed objects to a curing light from the curing light module 503.In exemplary embodiments, in order to facilitate movement of theplatform in and outside of the chamber 501, a drawer system 502 a may beemployed; such drawer system is discussed below with reference to otherfigures. In exemplary embodiments, the platform 502 includes a surfaceadapted to receive the 3D-printed object, the surface including: a mesh,or a material made of at least one of an ultraviolet C transparentmaterial and an ultraviolet A transparent material.

Curing light module 503 may be any light source or light source assemblyequipped with a light source suitable for post-curing 3D-printedobjects. In some exemplary embodiments, the light source assemblyincludes at least one light source disposed above the platform and atleast one light source disposed below the platform to maximize exposureto various portions of the 3D-printed object. In some exemplaryembodiments, the curing light module 503 comprises a Light EmittingDiode (LED) module 503 a for emitting the one or more wavelengths of thecuring light onto the 3D-printed object. LED module 503 a may becomprised of multiple LED panels, and in some exemplary embodiments, LEDmodule 503 a includes at least one LED panel disposed above the platform502 and at least one LED panel disposed below the platform 502. In orderto control a desired temperature inside the chamber 501 and also to keepoptimal performance of LED module 503 a, in some exemplary embodiments,LED module 503 a or curing light module 503 may include a thermalcontrol module 503 c built into a structure or light assembly of themodule; this may include a fan system to actively control a temperatureof the chamber and also of light source components of the curing lightmodule 503. In some exemplary embodiments, the curing light module 503comprises a lens system for volume coverage of the 3D printed object,the lens system including one or more convex lens adapted to moverelative to the light source assembly for changing a volume coveragearea of the 3D-printed object.

Movement module 504 may be any set of components that are suitable forfacilitating movement of curing light module 503 or platform 502. Forexample, and without limiting the scope of the present invention,movement module 504 may comprise a movement system for platform 501,such as a motor, actuator or device that moves platform 502. In someexemplary embodiments, a motor of the movement module may be configuredto rotate a turntable coupled to the platform. In some exemplaryembodiments, a motor, actuator or device may be configured to raise andlower the platform 502. In some exemplary embodiments, movement module504 may comprise a movement system for curing light module 503, such asa motor, actuator or device that moves one or more devices of the curinglight module 503; in some exemplary embodiments, this may involve amotor coupled to a pathway 504 a, such as a track, including a lineartrack, that enables movement of a light assembly along the pathwayinside the chamber. As will be discussed in more detail below, otherconfigurations are also possible—for example, and without limiting thescope of the present invention—movement module 504 may comprise ofmotors, actuators or devices that move both platform 502 and curinglight module 503. In exemplary embodiments, the movement module isadapted to facilitate at least one of continuous motion, motion havingmultiple stationary points, or bidirectional motion of the curing lightmodule 503 or the platform 502. In some exemplary embodiments, aposition sensor may be included in the movement module for determining aposition of a light source of the curing light module 503 or theplatform 502.

Processing module 505 may be any suitable computing device that isconfigurable or programmable with one or more executable instructionsconfigured to activate the various components of chamber 501. Generally,processing module 505 is configured to at least receive a user input,via a user interface 505 a coupled to the processing module 505, theuser input concerning the 3D-printed object and indicative of thepredetermined curing toolpath for post-curing the 3D-printed object;move the curing light module 503 or the platform 502 according to thecuring toolpath; and emit the curing light onto the 3D-printed objectalong the curing toolpath to create a post-cured 3D-printed object. Insome exemplary embodiments, a database in communication with theprocessing module that stores information about the 3D-printed object.

Turning now to the next figure, FIG. 3 depicts a flow chart of a methodin accordance with some exemplary embodiments of the present invention.More specifically, FIG. 3 depicts method 300 for selectively post-curinga 3D-printed object to attain variable properties. Although presented ina particular sequence, method 300 may be achieved in alternativesequences with optional steps, without deviating from or limiting thescope of the present invention. Generally, method 300 comprises thesteps of: 301 receiving data concerning a 3D-printed object; 302determining a curing toolpath configured to achieve a post-cured3D-printed object having variable properties along different regions ofthe post-cured 3D-printed object; and 303 selectively emitting a curinglight onto the 3D-printed object along the curing toolpath, whereincuring the 3D-printed object along the curing toolpath generates thevariable properties along the different regions of the 3D-printedobject.

In step 301, data concerning a 3D-printed object may be received. Thismay include receiving the data from a database or receiving the datafrom a 3D-scanner coupled to a system in accordance with the presentinvention. The data may be compiled by generating a digital model of the3D-printed object that divides the 3D-printed object as a number ofvolumes, wherein each of the divided volumes include a correspondingcuring position along the toolpath.

In step 302, a curing toolpath configured to achieve a post-cured3D-printed object having variable properties along different regions ofthe 3D-printed object may be determined. In exemplary embodiments, thismay be performed by the computer of the system. However, this step maybe performed externally to the system and the system may instead beconfigured to receive the data, which includes the desired curingtoolpath.

In step 303, the computer communicates with the light source and acuring light is selectively emitted onto the 3D-printed object inaccordance with the curing toolpath and the digital model, whereincuring the 3D-printed object along the curing toolpath generates thevariable properties along the different regions of the 3D-printedobject.

In some exemplary embodiments, a method for selectively post-curing a3D-printed object to attain variable properties may include the stepsof: mounting a 3D-printed object in a selective post-curing chamberincluding a post-curing light source configured to emit a curing lightonto the 3D-printed object; receiving data of the 3D-printed objectconcerning a curing toolpath and digital model of three-dimensionalprinted object; and selectively emitting a curing light onto the3D-printed object along the curing toolpath based on the model data,wherein curing the 3D-printed object along the curing toolpath generatesvariable properties along different regions of the 3D-printed object.

FIG. 4A exemplarily illustrates a perspective view of the chamber 400,according to an embodiment of the present invention. The chamber 400houses a post curing light source or movable light source assembly and amotion system, which will be discussed below with reference to otherfigures. FIG. 4B through FIG. 4E illustrate different views of themovable light source assembly that sits on a motion system withinchamber 400 in accordance with an exemplary embodiment of the presentinvention. The post curing system is configured to provide maximumirradiation, or volume coverage, of UVA light on the 3D-printed partsurface by using the motion system.

More specifically, FIG. 4A depicts movable light source assembly 202situated inside chamber 400. FIG. 4B-FIG. 4E depicts the movable lightsource assembly 202 in isometric view with several components: a bottomLED module including a bottom panel casing 430 a and a top LED moduleincluding a top panel casing 430 b, an LED casing connecting bracket402, and a motion system 202 a, which in some embodiments is a linearmotion system.

In some exemplary embodiments, the movable light source assembly 202 maybe coupled to linear motion system 202 a by way of a mounting bracket414 coupled between the movable light source assembly 202 and linearmotion system 202 a, and a connecting bracket 416 that couples themounting bracket 414 to a portion of the mounting bracket 414 such as atrack (or for example, a lead screw 404). Linear motion system 202 a maycomprise of a high accuracy stepper motor 410 (see FIG. 4D, forexample), a lead screw 404, a linear guide 406, a linear guide mountingplate 408 and a position sensor 412. The high-power LED modules may beheld together by the bracket 402, which is connected to the motionsystem 202 a for linear guidance—or so hat the movable light sourceassembly 202 may be positioned along a track of the motion system 202 a.A cable track may be used to enable one dimensional freedom for thepower cables.

The LED module may include uniform light intensity along the X axis andthe linear motion system creates motion along the Y axis to increase thevolume coverage. The motion can be either a continuous motion or havemultiple stationary points. The length of the movement may be dividedinto different zones according to the number of models present forcuring and, in some embodiments, may be indicated on a mounting platformsuch as a tray holder 444, shown in FIG. 9C, for a user's reference.

In another exemplary embodiment of the present invention, the postcuring system may contain a movement system for volume coverage achievedby linear uniaxial motion in the X or Y axis. The volume coverage mayalternatively be achieved by implementing a rotational motion. The LEDmodule and bracket system are connected to the motor system to createrotational motion. The LEDs uniformly irradiate the radial direction,and the rotational motion covers the entire platform area.Alternatively, volume coverage may be achieved by fixed light source anda moving platform. For the linear movement system, it may be achieved bymoving the platform in the X or Y axis. The volume coverage may also beachieved by implementing a turntable, where the light source is fixedbut the platform moves. Another alternative for volume coverage isbidirectional motion. This involves combining motion in the X and Yaxis.

In another exemplary embodiment of the present invention, the volumecoverage may alternatively be achieved by tilting a light source. Thesystem may include a high optical power light source which is rotatedabout an axis, which is either on the light source or away from it. Thedistance from the axis determines the optical output required from thepanel.

In another exemplary embodiment of the present invention, a desirablevolume coverage may be achieved by use of a convex lens system. Thesystem may include a high-power LED source accompanied by a convex lens.The optical output from the high-power LED source passes through theconvex lens. The lens is moved closer or further away from the source tochange the coverage area. In another exemplary embodiment, the lightsource is moved relative to the lens.

In exemplary embodiments, the LED module or modules may be adapted tousing multiple wavelengths of light in different combinations to givethe 3D-printed objects varying desired physical properties. For example,and without limiting the scope of the present invention, multiple curingwavelength may involve UVA+UVC, or other combinations to selectivelyenhance the properties of the 3D-printed parts being cured withinchamber 400.

FIG. 5 exemplarily illustrates an exploded view of the light sourceassembly, according to an embodiment of the present invention. The lightsource assembly consists of a top LED panel casing 430 b and bottom LEDpanel casing 430 a, which house LED panels 418 and 420, respectively,including heat sinks 426. The bottom LED panel casing 430 a houses thebottom LED panel 420 and the top LED panel casing 430 b houses the topLED panel 418. Each casing is designed to accommodate the heat sink 426between the wall of the casing (430 a, 430 b) and respective heat sink426 which ensures that an airflow is directed through the heat sink byway of a fan system (for example, and without limitation, fans 422) thatfacilitates the airflow. The transition from the circular cross sectionof the fan to the rectangular cross section of the duct is enabled usinga fan mounting spacer 428 which may be designed with smooth surfaces andgradual transition and the fan 422 may be centered with the duct toreduce pressure drop, eliminating vortex formation and removing zonesfor pressure drops. Openings at each terminal end of each casing mayform a duct that may include caps (424 a, 424 b) to prevent exposure tothe heat sink. Each cap (424 a, 424 b) may include an opening on thesides and perforations on the top to further facilitate airflow. Thetotal area of openings through these is equal to the cross-sectionalarea of the duct, to reduce pressure drop. The fan 422 orientation canbe either a high static pressure fan, or multiple fans in series togenerate high static pressure than single fan at similar flow rate ofsingle fan or multiple fans in parallel to generate same static pressureas single fan but with a higher flow rate.

FIG. 6 exemplarily illustrates an exploded view of an LED module (inthis case the top LED module that is secured or housed within top panelcasing 430 b) in accordance with the present invention, which employs athermal management system, as will be discussed further below. The LEDmodule includes a plurality of LEDs disposed on a surface of the LEDpanel 418, thermal pad 432, and a heat sink 426. A bottom LED module mayinclude a similar mirrored configurations of LED panel, thermal pad, anda heat sink.

Because some of the photopolymers to be post cured within chamber 400may require an ambient temperature of 60 Celsius, air inside the chambermay need to be heated. On the other hand, the UVA LEDs typically have anoperating efficiency of 59% and may generate waste heat of 48 Watt forthe top panel and 19 Watt for the bottom panel, with a potential maximumjunction temperature for a UVA LED 90 Celsius and for UVC LED 100Celsius. Thus, there is also a need to cool down the LED panel. Toaddress these factors, in exemplary embodiments, a cooling system forLEDs may include several components: heat sink 426, thermal pad 432, andcooling fan 422—all housed within each of the LED panel casing 430 thatfacilitates air circulation between the top and bottom LED panels. Insome exemplary embodiments, the size of the top LED panel 418 and thebottom LED panel 420 may be 224 mm by 60 mm. A single layer aluminum PCBmay be used to make the LED panel. This helps decrease the thermalresistance from the board and provides a large surface area for the heatto transfer. The ambient temperature in the chamber 400 may bepreferably at 60 Celsius and the LED junction temperature may bepreferably below 80 Celsius, which gives a delta T of 20° C. The heatoutput from the panel may be 48 Watt, hence the maximum thermalresistance for the system is preferably below 0.42 C/W, which iscalculated by using Formula (7) and Formula (8):

Thermal resistance=Desired delta T÷Heat Output  (Formula (7)),

Q=hc A(Ts−Ta)  (Formula (8)),

where Q is the rate of heat transfer; hc is the convection heat transfercoefficient; A is surface area for heat transfer; Ts is the surfacetemperature of heat sink; and Ta is the air temperature.

In exemplary embodiments, chamber 400 may employ specific materials tomaximize a reflectance for the UV light output from movable light sourceassembly 202. For example, and without limiting the scope of the presentinvention, the materials may include Aluminum, Stainless Steel or Teflon(Porex). In some exemplary embodiments, chamber 400 may employ a surfacefinish to maximize the reflection. For example, and without limiting thescope of the present invention, the surface finish may include enhancedAluminum, and or titanium oxide coating. Of course, other materials andor combination of materials may be employed in order to improve ormaximize a desired reflectance for the UV light output from movablelight source assembly 202. Accordingly, in exemplary embodiments, camber400 comprises a surface finish to maximize the reflection.

FIG. 7 exemplarily illustrates a heating device arranged in the chamber400, according to an embodiment of the present invention. FIG. 8exemplarily illustrates an exploded view of the heating device of thechamber 400, according to an embodiment of the present invention, whichreaches a desirable temperature for curing certain photopolymers.

The heating device 438 includes a heating element 438 a configured totransfer heat energy to the air in the least amount of time. Heatingdevice 438 may be an electric heater employing a heating element thatoutputs heat distributed in two parts. The first part may be responsiblefor heating the heating element and the second part may be responsiblefor transferring heat to the air inside the chamber. In exemplaryembodiments, heating element 438 a may be adapted to have minimumthermal lag, i.e., reaching an operating temperature in minimum amountof time. The thermal lag depends on the mass and the specific heat ofthe material used in heating device 438. In some exemplary embodiments,an outer shell ma be made of stainless steel which under hightemperature forms a layer of Cr2O3 that resists further oxidation of theheating element. In some exemplary embodiments, a resistive wire my beused; for example a nichrome ire capable of withstanding hightemperature may be covered by a sheath of MgO that acts as an electricalinsulator. In some embodiments, the heating device may use metal ceramicelements. In some embodiments, heating element 438 a is a bare nichromewire. In some embodiments, heating element 438 a is a nichrome wire in ametal casing. In some embodiments, heating device 438 includes resistivenichrome wires infused in aceramic casing. The heating elementpreferably has very low oxidation; to these ends, a ceramic surface maybe employed.

FIG. 8 illustrates an exemplary embodiment of the present invention inwhich the heating element 438 a attains high surface temperature, inexcess of 418 Celsius. The heating element 438 a needs to be isolatedfrom the user because of the high temperature. The heater housing 436has been designed to contain and redirect the airflow into the chamber400. The housing has an insulation (440 and 442) wrap on the exterior.One side of the heater housing has a threaded mounting hole. The heateris screwed into the hole. The side panels 434 of the heater housing hastabs 472 on its sides which fits into the grooves 474 in the heaterhousing 436 disposed at the bottom portion. The side panels 434 havespacers to ensure that the side insulation 440 does not get pressedduring the assembly. The heater housing is positioned on the bottom ofthe chamber 400 to facilitate natural convection. The heater housing iscovered by protective mesh, the size of mesh is to maximize the airflow.In some exemplary embodiments, a sheet metal may be used to offer littleresistance to transfer of heat from inside the product to outside.

Turning now to the next set of figures, FIG. 9A through FIG. 9Gillustrate perspective views of a post curing system in accordance withan exemplary embodiment of the present invention. More specifically,FIG. 9A and FIG. 9B show a front view and an isometric view,respectively, of an exemplary embodiment of a post curing system. Due tothe large surface area, the chamber acts like a heat sink and dissipatesheat away. To further reduce heat waste, a layer of insulation 468 maybe added to the outer wall of the inner enclosure 466 (see FIG. 9A-9B,for example). The insulation layer 468 may be characterized by an Rvalue which describes the temperature difference across the insulationfor a unit heat flux. The requirement for the chamber may be that theexternal enclosure temperature stays below 37 Celsius, the bodytemperature. Another attribute required of the insulation may be to havea flame rating of 0 or 1 according to NFPA.

As the chamber heats up air to higher temperatures, the enclosure maybecome hot and dangerous to handle. To solve this issue, the chamber mayemploy two sections. An inner section formed by inner enclosure 466 thatencloses the LED module and the heating device; this section heats upduring the operation to a temperature of 60 Celsius. And an outersection formed by an outer enclosure 458 may include an insulationmaterial to contain the heat; the insulation material selected has Rvalue such that the temperature on the outer chamber 458 is reduced tobelow 37 Celsius, which is the body temperature. This prevents exposureto hot bodies for the user. The inner enclosure 466 may be coupled tothe outer enclosure 458 by way of one or more supports 464 that securethe inner enclosure within an interior region of the outer enclosure458, leaving a space between the outer enclosure 458 and inner enclosure466. As may be appreciated from the view of FIG. 9B, the outer enclosure458 may optionally include one or more LCD cutouts 470 disposed over thetop surface of the outer enclosure 458 for displaying one or moreindication lights to the user indicative of a status of the device orpost-curing process. In some exemplary embodiments, the top surface ofouter enclosure 458 is smooth and excludes the LCD cutouts (see forexample FIG. 9C).

FIG. 9C through FIG. 9F show perspective views of a drawer system inaccordance with an exemplary embodiment of the present invention. Insome exemplary embodiments, chamber 400 may employ a drawer system thatfacilitates access to a platform such as a mounting platform formounting or positioning 3D-printed objects within chamber 400. Inexemplary embodiments, the drawer system is aimed at maximizing a usablearea while minimizing the overall footprint. The drawer system mayemploy a push to close design which locks at the close position.

In some exemplary embodiments, the drawer system comprises a front cover454 that may be made of a UV blocking material. The drawer design mayimplement an opening height to restrict the height of the model to amaximum permissible height. This ensures no contact between the LEDpanels (418, 420 inside chamber 400) and the 3D-printed object situatedwithin a platform (such as a tray) of the drawer system. The drawersystem may employ a magnetic sensor to detect the state of the drawer,which offers a safety switch that switches off the heater device and theUV LEDs when the drawer is opened. In exemplary embodiments, the drawersystem comprises: a drawer 460, which includes a door with a handle 452,a front cover 454 and front panel 456 that provide UV shielding aroundthe opening into the chamber 400, and a tray system including a trayholder 444 that sits within a portion of drawer 460, a tray handle 446and a tray mesh 448. The drawer system enables a platform, such as trayor tray mesh 448, to entirely slide out of chamber 400. The tray mesh448 may be placed on tray holder 444 which is connected to a drawerslider 450. The tray handle 446 enables the user to lift the tray to addconvenience while placing the 3d-printed objects or modes onto theplatform or tray mesh 448. In exemplary embodiments, such as the oneshown in these views, includes a platform configured to enable exposureto curing light from above as well as from underneath the platform. Forexample, and without limiting the scope of the present invention, traymesh 448 may comprise a plurality of openings that facilitate exposureto UV light from the bottom or below the 3D-printed objects that aredisposed on tray mesh 448. In some exemplary embodiments, a UVC and UVAtransparent material may be used to form the base of the platform. Insome exemplary embodiments, tray mesh 448 has a large open area to totalarea percentage of 58%. As can be appreciated from FIG. 9D, supports462, such as frictional supports that may include, without limitation,rubber feet, may be utilized as a support mechanism that prevents theouter enclosure from sliding or moving during use.

FIG. 9G shows an isometric view of a front panel in accordance with anexemplary embodiment of the present invention. In exemplary embodiments,the front cover 454 is modular; it may be coupled to the front panelusing location pins to constraint the movement parallel to the frontpanel 456 and magnets to constraint movement perpendicular to the frontpanel 456. Alternatively, fasteners can be used to make the front coveraccessible. This enables the user to disassemble the front cover 454 andperform cleaning operations on the part.

FIG. 10 and FIG. 11 illustrate graphs (1000, 1100) of radiation patternsfor a post curing system in accordance with an exemplary embodiment ofthe present invention. In the exemplary embodiment, the post curingsystem provides uniform curing using two factors that result indifferent intensities and different points on the trays: the lightsource and the light intensity. The light source, UV LEDs have acharacteristic radiation pattern which provides the curve for relativepower output vs angle. This brings a gradient of optical power incidenton the illuminated area. The light intensity is inversely proportionalto the square of distance between the measurement point and the lightsource. This is the second source of non-uniformity on the illuminatedarea.

In another exemplary embodiment of the present invention, the postcuring system uses UVA LED with viewing angle 120 degrees and UVC LEDwith viewing angle of 60 degrees. The viewing angle is described as theangle made with normal to the LED at which the relative optical poweroutput is 50% of the maximum. The layout for the LED has been designedkeeping in mind requirements for uniformity on the illuminated area. Thedistribution was transformed to relative optical power output vs solidangle. The formula used for translating 2-D angle to solid angle isFormula (1). A cartesian coordinate system was chosen to factor in thedistance from the light source. The distance and angle between lightsource and reference point was obtained using the coordinate systemusing Formula (2). The intensity at reference point is found using theFormula (3). These formulas are as follows:

Ω=2π(1−cos θ)  Formula (1);

D=√((x1−x2){circumflex over ( )}2+(y1−y2){circumflex over( )}2+(z1−z2){circumflex over ( )}2)  Formula (2);

I0*Σ(ΔΩi*xi)=P/r{circumflex over ( )}2  Formula (3);

where D is the distance between two points; x1,y1,z1 are the location ofthe LED in cartesian coordinate system; x2, y2, z2 are location ofreference point in cartesian coordinate system; I0 is the irradiance;ΔΩi is the solid angle coverage; and Xi is the intensity factor for thesolid angle coverage.

The total intensity at the reference point was calculated usingsuperposition theorem and is the sum of intensities from all the LEDs atthe point. The LEDs are distributed with higher densities near the endand in the center to make the sum of intensities uniform across theilluminated area. The uniformity data from the panel is as follows. TheLED distribution also focuses on the heat generated by the LEDs. Theconcentration of LEDs on the ends is limited by the amount of heatgenerated locally on the edges and the ability to dissipate the heatefficiently. The heat flux was limited to 1 Watt/cm2.

FIG. 12 illustrates a graph 1200 of relative intensity of light sourceof bottom and top panel, according to an embodiment of the presentinvention. FIG. 13 illustrates a graph 1300 of energy absorption for apost curing system in accordance with an exemplary embodiment of thepresent invention. The photopolymers have photoinitiators which eitherthrough radical formation or cationic initiation, initiate thepolymerization. The photoinitiator absorbs energy from the UV light toform free radicals which causes the reaction. The photoinitiators usedin photopolymers have a local maxima in absorbance at 365 nm wavelengthand the absorbance decreases below 0.1 at wavelength above 420 nm. Theabsorption gives the efficiency of curing. To decide the optimalwavelength, the overall efficiency was calculated by multiplying theoperating efficiency of the LED by the efficiency of curing, shown inFormula (4) and (5).

Operating efficiency=(Optical Power Output)÷(Forward voltage*Forwardcurrent)  Formula (4);

Overall efficiency=Operating efficiency*Wavelength efficiency  Formula(5).

FIG. 14 illustrates a graph 1400 for absorbance of UVC by e-colibacteria in accordance with an exemplary embodiment of the presentinvention. UV light below 280 nm in wavelength destroys nucleic acid inthe microorganisms and kills them by disrupting their DNA. Theefficiency of destroying nucleic acid depends on the absorption of UVlight of different wavelengths. Prior research shows that the absorptionof UV has local minima at around 255 nm (25% absorption) and it is muchhigher at lower wavelengths (greater than 27% below 235 nm). While theefficiency of disinfection increases as the wavelength is decreased,wavelengths below 240 nm cause photolysis of oxygen to ozone which isnot desired. The primary sources of UVC light are, low pressure/highpressure mercury lamps, excimer lamps and LEDs. The product uses UVCLEDs as the light source. UV LEDs with wavelength ranging from 265 to280 nm were evaluated and the overall efficiency was used as a factor todetermine the optimal wavelength. The LED system had two differentefficiencies, the operating efficiency and the absorption efficiency fornucleic acid. The overall efficiency was obtained as a product of thetwo efficiencies.

In another exemplary embodiment of the present invention, a common issuewith UVC disinfection devices is the inability to disinfect in thepresence of undercut regions. The product focuses on disinfecting thesurface of printed models and reduces the event of shadow regions byusing two light sources, one from the bottom LED panel 420 and one fromthe top LED panel 418. Turning to the next set of figures, FIG. 15 andFIG. 16 show graphs (1500, 1600) of UVC intensity of a post curingsystem in accordance with an exemplary embodiment of the presentinvention. The disinfection depends on the energy that is delivered tothe desired surface. The data published by FDA recommends a dosage of186 mJ/cm2 for Log 4 level sterilization. According to our experiments,300 mJ/cm2 dosage was needed for a log 2 sterilization of the surface.The intensity for UVC at the target area was calculated using Formula(6):

I0*Σ(ΔΩi*xi)=P/r{circumflex over ( )}2  Formula (6);

where I0 is the irradiance; ΔΩiis the solid angle coverage; and Xi isthe intensity factor for the solid angle coverage.

More specifically, FIG. 15 shows one exemplary embodiment of the presentinvention, in which superposition theorem was used to determine thecombined intensity at the target area. The uniformity across the targetarea is shows in FIG. 15 . This gave a disinfection time performancecurve as shown in FIG. 16 , which was calculated by dividing the targetdosage by the intensity.

FIG. 17 illustrates another exemplary embodiment of the presentinvention in which the rate of heat transfer is directly proportional tosurface area in contact with the air. Heat sink 426 is used to increasethe surface area for heat transfer. The second factor in the heattransfer equation is the convection coefficient which depends on theairflow velocity. The thermal resistance and the airflow temperaturecharacteristic curve for the heat sink is shown in graph 1700 of FIG. 17. The pressure drop due the heat sink is also a function of the airflowvelocity. The heat sink 426 has optimized elliptical shaped fins tofacilitate airflow and decrease the pressure drop across the heat sinkwhile maintaining high surface area for heat transfer.

In another exemplary embodiment of the present invention, the heat sink426 and aluminum PCB have machined surfaces but to have the best heattransfer between the surfaces, an interface material needs to be used inbetween them. The interface material has high thermal conductivity andgoes into the void to fill any gaps between the two surfaces. Thematerial used can be thermal grease, which when pressed between the twosurfaces can go into the void or a phase changing material which actslike a sheet under room temperature but changes its shape under highertemperature to flow in and fill the gaps. The alternative materialchoice which is being used in the product is thermal pad 432 which is asoft sheet which is sandwiched between the heat sink 426 and thealuminum PCB.

FIG. 18 illustrates another exemplary embodiment of the presentinvention in which the LED heat dissipation relies on forced convection.The relation between the airflow and the heat dissipation is given bygraph 1800. The fan statistic curve or static pressure curve provides arelation between the pressure drop and the volumetric flow rate. Theoperating point for the fan 422 is the intersection of the fan staticpressure curve and the system pressure curve. The system pressure curveis the pressure drop across the system, which in the products case isthe sum of pressure drop across the heat sink, the front cap and frontand back walls of the chamber 400. This is shows by Formula (9):

System Resistance Curve=Pressure drop across(Heat Sink+FrontCap+Wall atInlets and Outlets)  Formula (9).

Based on the airflow vs pressure drop curve for heat sink and the staticpressure curve, the operating point for the fan is decided.

A system and method for selectively post curing 3D objects printed withstereolithography additive manufacturing techniques has been described.The foregoing description of the various exemplary embodiments of theinvention has been presented for the purposes of illustration anddisclosure. It is not intended to be exhaustive or to limit theinvention to the precise form disclosed. Many modifications andvariations are possible in light of the above teaching without departingfrom the spirit of the invention.

What is claimed is:
 1. A system for post-curing a three-dimensionallyprinted (3D-printed) object, comprising: a chamber; a platform arrangedwithin the chamber for supporting at least one 3D-printed object; alight source assembly configured to emit one or more wavelengths ofcuring light onto the 3D-printed object, wherein the light sourceassembly includes at least one first light source configured toilluminate the 3D-printed object from a first direction and at least onesecond light source configured to simultaneously illuminate the3D-printed object from a second direction, the second direction distinctfrom the first direction; a movement module configured to move the lightsource assembly, or the platform, to expose different regions of the3D-printed object to the curing light.
 2. The system of claim 1, whereinthe second direction is opposite the first direction.
 3. The system ofclaim 1, wherein the at least one first light source is disposed abovethe platform.
 4. The system of claim 1, wherein the at least one secondlight source is disposed below the platform.
 5. The system of claim 1,wherein the at least one first light source is disposed above theplatform and the at least one second light source is disposed below theplatform.
 6. The system of claim 1, wherein the second direction isorthogonal to the first direction.
 7. The system of claim 1, wherein thesecond direction is at an acute angle with respect to the firstdirection.
 8. The system of claim 1, wherein the second direction is atan obtuse angle with respect to the first direction.
 9. The system ofclaim 1, wherein the movement module is configured to move the first andsecond light sources simultaneously.
 10. The system of claim 1, whereinthe platform includes a surface adapted to receive the 3D-printedobject, the surface including: a mesh, or a material made of at leastone of an ultraviolet C transparent material and an ultraviolet Atransparent material.
 11. The system of claim 1, wherein the lightsource assembly comprises a Light Emitting Diode (LED) module foremitting the one or more wavelengths of the curing light onto the3D-printed object.
 12. The system of claim 1, wherein the light sourceassembly comprises a lens system for volume coverage of the 3D printedobject, the lens system including one or more convex lens adapted tomove relative to the light source assembly for changing a volumecoverage area of the 3D-printed object.
 13. The system of claim 1,wherein the movement module is adapted to facilitate at least one ofcontinuous motion, motion having multiple stationary points, orbidirectional motion of the light source assembly or the platform. 14.The system of claim 1, wherein the movement module comprises a linearmotion system coupled to the light source assembly to facilitatemovement of the light source assembly along a length within the chamber.15. The system of claim 1, wherein the movement module is configured torotate the light source assembly or the platform.
 16. The system ofclaim 1, wherein the movement module is configured to tilt the lightsource assembly or the platform.
 17. The system of claim 1, wherein themovement module includes a position sensor for determining a position ofthe light source assembly or the platform.
 18. The system of claim 1,wherein the platform includes a drawer system for facilitating insertionand removal of the platform in and out of the chamber.
 19. The system ofclaim 1, further comprising a heating element situated inside thechamber.
 20. The system of claim 19, wherein the heating elementincludes resistive nichrome wires infused in a ceramic casing.